The present disclosure relates to a fixing device configured to fix a toner image on a sheet and an image forming apparatus provided with the fixing device.
An electrographic image forming apparatus, such as a copying machine and a printer, is usually provided with a fixing device configured to fix a toner image on a sheet. The fixing device includes a heating member (for example, a heating roller or a heating belt) and a pressing member (for example, a pressing roller or a pressing belt) configured to come in pressure-contact with the heating member. And, by heating and pressing the sheet and the toner image at a fixing nip formed between the heating member and the pressing member, the toner image is fixed on the sheet.
The fixing device of such a configuration is provided with a separating member which comes in contact with the heating member or faces the heating member at intervals. And, the sheet with the fixed toner image is separated from the heating member by using the separating member.
In the fixing device of such a configuration, the toner (developer)) on the sheet may be attached and then deposited on the separating member. When the toner is deposited on the separating member in this way, the deposited toner may move to the heating member and cause a damage to the heating member. Alternatively, the toner deposited on the separating member may move to the sheet and cause an image degradation.
Thus, there is a configuration that both a front surface (a surface configured to guide the sheet) and a back surface (a surface configured to face the heating member) of the separating member are coated with fluoroethylene resin to prevent attaching of the toner on the separating member. Alternatively, there is another configuration that a sheet member is attached on the separating member to prevent attaching of the toner on the separating member.
In the configuration that the both the front and back surfaces of the separating member are coated with fluoroethylene resin, when a part of the back surface of the separating member is not coated with fluoroethylene resin, the toner may attach and deposit on the part having no fluoroethylene resin coating. And, it is difficult to coat the front surface and the back surface of the separating member with a constant thickness at a time. In addition, when the coating of the front surface and the back surface of the separating member would be carried out at a time, a coating pool may be caused easily. Therefore, in order to coat the front surface and the back surface of the separating member with a consistent thickness without causing a coating pool, it is necessary to carry out the coating in several times. This leads a complication of the coating process and increase of a unit price of the separating member.
On the other hand, the configuration that the sheet member is attached on the separating member requires use of the sheet member in addition to the separating member, causing increase of the number of members and cost.
Furthermore, if the configuration that the both surfaces of the separating member are coated with fluoroethylene resin and another configuration that the sheet member is attached on the separating member may be applied, it is difficult to perfectly prevent attaching of the toner on the separating member and thereby it is required to clean the separating member. When the cleaning of the separating member may be not easily carried out, the toner deposited on the separating member may move to the heating member and cause a damage to the heating member. Alternatively, the toner deposited on the separating member may move to the sheet and cause an image degradation.